feat: add Unity 6 client with 2.5D visual system

Unity client features:
- WebSocket connection via NativeWebSocket
- 2.5D agent visuals with programmatic placeholder sprites
- Billboard system for sprites and UI elements
- Floating UI panels (name, HP, energy bars)
- Speech bubble system with pop-in animation
- RTS-style camera controller (WASD + scroll zoom)
- Editor tools for prefab creation and scene setup

Scripts:
- NetworkManager: WebSocket singleton
- GameManager: Agent spawning and event handling
- AgentVisual: 2.5D sprite and UI creation
- Billboard: Camera-facing behavior
- SpeechBubble: Animated dialogue display
- CameraController: RTS camera with UI input detection
- UIManager: HUD and command input

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

unity-client/Assets/Prefabs/AgentPrefab.prefab

@@ -0,0 +1,176 @@
+%YAML 1.1
+%TAG !u! tag:unity3d.com,2011:
+--- !u!1 &1907814268248440061
+GameObject:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  serializedVersion: 6
+  m_Component:
+  - component: {fileID: 5646202202797632544}
+  - component: {fileID: 5061177960749080548}
+  m_Layer: 0
+  m_Name: Sprite
+  m_TagString: Untagged
+  m_Icon: {fileID: 0}
+  m_NavMeshLayer: 0
+  m_StaticEditorFlags: 0
+  m_IsActive: 1
+--- !u!4 &5646202202797632544
+Transform:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 1907814268248440061}
+  serializedVersion: 2
+  m_LocalRotation: {x: 0, y: 0, z: 0, w: 1}
+  m_LocalPosition: {x: 0, y: 0, z: 0}
+  m_LocalScale: {x: 1, y: 1, z: 1}
+  m_ConstrainProportionsScale: 0
+  m_Children: []
+  m_Father: {fileID: 9065057861111836059}
+  m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
+--- !u!212 &5061177960749080548
+SpriteRenderer:
+  serializedVersion: 2
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 1907814268248440061}
+  m_Enabled: 1
+  m_CastShadows: 0
+  m_ReceiveShadows: 0
+  m_DynamicOccludee: 1
+  m_StaticShadowCaster: 0
+  m_MotionVectors: 1
+  m_LightProbeUsage: 1
+  m_ReflectionProbeUsage: 1
+  m_RayTracingMode: 0
+  m_RayTraceProcedural: 0
+  m_RayTracingAccelStructBuildFlagsOverride: 0
+  m_RayTracingAccelStructBuildFlags: 1
+  m_SmallMeshCulling: 1
+  m_ForceMeshLod: -1
+  m_MeshLodSelectionBias: 0
+  m_RenderingLayerMask: 1
+  m_RendererPriority: 0
+  m_Materials:
+  - {fileID: 10754, guid: 0000000000000000f000000000000000, type: 0}
+  m_StaticBatchInfo:
+    firstSubMesh: 0
+    subMeshCount: 0
+  m_StaticBatchRoot: {fileID: 0}
+  m_ProbeAnchor: {fileID: 0}
+  m_LightProbeVolumeOverride: {fileID: 0}
+  m_ScaleInLightmap: 1
+  m_ReceiveGI: 1
+  m_PreserveUVs: 0
+  m_IgnoreNormalsForChartDetection: 0
+  m_ImportantGI: 0
+  m_StitchLightmapSeams: 1
+  m_SelectedEditorRenderState: 0
+  m_MinimumChartSize: 4
+  m_AutoUVMaxDistance: 0.5
+  m_AutoUVMaxAngle: 89
+  m_LightmapParameters: {fileID: 0}
+  m_GlobalIlluminationMeshLod: 0
+  m_SortingLayerID: 0
+  m_SortingLayer: 0
+  m_SortingOrder: 0
+  m_MaskInteraction: 0
+  m_Sprite: {fileID: 0}
+  m_Color: {r: 1, g: 1, b: 1, a: 1}
+  m_FlipX: 0
+  m_FlipY: 0
+  m_DrawMode: 0
+  m_Size: {x: 1, y: 1}
+  m_AdaptiveModeThreshold: 0.5
+  m_SpriteTileMode: 0
+  m_WasSpriteAssigned: 0
+  m_SpriteSortPoint: 0
+--- !u!1 &3706388644011989616
+GameObject:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  serializedVersion: 6
+  m_Component:
+  - component: {fileID: 9065057861111836059}
+  - component: {fileID: 5704205502650767077}
+  - component: {fileID: 4731420257141751864}
+  m_Layer: 0
+  m_Name: AgentPrefab
+  m_TagString: Untagged
+  m_Icon: {fileID: 0}
+  m_NavMeshLayer: 0
+  m_StaticEditorFlags: 0
+  m_IsActive: 1
+--- !u!4 &9065057861111836059
+Transform:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 3706388644011989616}
+  serializedVersion: 2
+  m_LocalRotation: {x: 0, y: 0, z: 0, w: 1}
+  m_LocalPosition: {x: 0.35356, y: 0.24749, z: 0.35356}
+  m_LocalScale: {x: 1, y: 1, z: 1}
+  m_ConstrainProportionsScale: 0
+  m_Children:
+  - {fileID: 5646202202797632544}
+  m_Father: {fileID: 0}
+  m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
+--- !u!136 &5704205502650767077
+CapsuleCollider:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 3706388644011989616}
+  m_Material: {fileID: 0}
+  m_IncludeLayers:
+    serializedVersion: 2
+    m_Bits: 0
+  m_ExcludeLayers:
+    serializedVersion: 2
+    m_Bits: 0
+  m_LayerOverridePriority: 0
+  m_IsTrigger: 0
+  m_ProvidesContacts: 0
+  m_Enabled: 1
+  serializedVersion: 2
+  m_Radius: 0.5
+  m_Height: 2
+  m_Direction: 1
+  m_Center: {x: 0, y: 0, z: 0}
+--- !u!114 &4731420257141751864
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 3706388644011989616}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: d8a016bdb4b93424da387c520b59cbfb, type: 3}
+  m_Name: 
+  m_EditorClassIdentifier: Assembly-CSharp::TheIsland.Visual.AgentVisual
+  characterSprite: {fileID: 0}
+  spriteColor: {r: 1, g: 1, b: 1, a: 1}
+  spriteScale: 2
+  sortingOrder: 10
+  placeholderBodyColor: {r: 0.3, g: 0.6, b: 0.9, a: 1}
+  placeholderOutlineColor: {r: 0.2, g: 0.4, b: 0.7, a: 1}
+  uiOffset: {x: 0, y: 2.2, z: 0}
+  uiScale: 0.008
+  speechDuration: 5
+  speechOffset: {x: 0, y: 3.5, z: 0}
+  hpHighColor: {r: 0.3, g: 0.9, b: 0.3, a: 1}
+  hpLowColor: {r: 0.9, g: 0.3, b: 0.3, a: 1}
+  energyHighColor: {r: 1, g: 0.8, b: 0.2, a: 1}
+  energyLowColor: {r: 1, g: 0.5, b: 0.1, a: 1}

unity-client/Assets/Prefabs/AgentPrefab.prefab.meta

@@ -0,0 +1,7 @@
+fileFormatVersion: 2
+guid: cd2ef4e78ca4d4328a27162d4ea50b6f
+PrefabImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: